atom" and then adds: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly , 1=''?''_{hfs Cs} = {{val}}." The dimension of the unit hertz is 1/time (T^-1). Expressed in base SI units, the unit is the reciprocal second (1/s).

In English, "hertz" is also used as the plural form. As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, ), MHz (megahertz, ), GHz (gigahertz, ) and THz (terahertz, ). One hertz (i.e. one per